JPH07216303A - Chipping-resistant topcoating composition and method for forming coating film therefrom - Google Patents

Abstract

PURPOSE:To obtain a topcoating composition capable of forming a film having high gloss and satisfactory chipping resistance. CONSTITUTION:This topcoating composition comprises 100 pts.wt. isocyanate- curable resin and 80-120 pts.wt. barium sulfate having an average particle diameter of 0.1-1mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chipping-resistant top coating composition and a method for forming a coating film thereof.

[0002]

2. Description of the Related Art Conventionally, the floors and the like of the body of an automobile are splashed by pebbles, gravel, rock salt, etc. sprinkled in the winter when the automobile is running, and are scratched when hitting the floor or the like of the automobile. When it is attached, rust is generated, and further progresses, large defects such as holes are generated. Chipping resistant paints are commonly used to prevent this defect.

Such chipping-resistant paint is applied not only to the underfloor, but also to other parts of the body of an automobile, for example, the outer plate part such as the front apron, front fender, rocker panel, door, rear fender, and parts around the feet. Has been done.

As an anti-chipping paint for automobiles,
Solvent-free paints using vinyl chloride plastisol resins, solvent-based paints using polyurethane resins, epoxy resins, etc. or water-based paints containing water-based emulsion resins as main components are known.

[0005] In recent years, the service life of vehicles has been extended and the level of rust prevention has been increased. With this trend, market needs for chipping-resistant paints have been increasing to increase the coating area and the coating thickness.

On the other hand, in order to save energy in automobiles, it is required to improve the fuel efficiency and to reduce the weight of the body.

In order to meet such market needs, it is required to reduce the coating weight of the chipping-resistant paint, and in order to meet this demand, a method using a hollow filler has been proposed. The outer skin of the automobile is finished with a chipping-resistant paint with an intermediate coat and a top coat. on the other hand,
In large-scale industrial machinery, such as power shovels and crane trucks, phthalic acid-based primer or two-component urethane paint is usually applied on phthalic acid-based primer.
No chipping resistance was required. However, in recent years, industrial machines that handle pebbles, gravel, earth and sand, etc. have become more compact and multicolored, and the same chipping resistance as automobiles has become required, and this is a thick film-type primer and topcoat coating that also saves labor. Is required.

[0008]

SUMMARY OF THE INVENTION The inventors of the present invention have found that a coating composition prepared by blending an isocyanate-curable resin with barium sulfate having an average particle size of 0.1 to 1 μm in a specific ratio has chipping resistance, finishability, etc. It was found that the present invention provides an excellent coating film, and completed the present invention.

That is, 80 to 120 parts by weight of barium sulfate having an average particle diameter of 0.1 to 1 .mu.m is mixed with 80 to 120 parts by weight of an isocyanate-curable resin per 100 parts by weight of the above resin, in a chipping-resistant top coating composition and an article to be coated, The above chipping-resistant top coating composition is cured to a coating film thickness of 50 to 300 μm.
This is related to the method of forming a coating film by spraying so as to have a size of m.

The isocyanate-curable resin used in the coating composition of the present invention contains a polyol and a polyisocyanate as a curable resin component.

The above-mentioned polyol is preferably a base resin having an average molecular weight of about 1,000 to 30,000 and an average of about 5 to 50 hydroxyl groups in one molecule. If the average molecular weight is less than about 1,000, a highly glossy coating film cannot be obtained. On the other hand, when it exceeds about 30,000, atomization of the coating material by spray coating becomes poor and the appearance of the coating film becomes poor, which is not preferable. On the other hand, if the number of hydroxyl groups is less than about 5 on average, a tough coating film having many network bonds cannot be obtained. On the other hand, if it exceeds about 50, the pot life becomes short and the cost becomes high, which is not preferable. Further, the polyol may contain a carboxyl group as required.

Examples of the polyol include acrylic polyol, polyester polyol, polyether polyol and the like.

Acrylic polyols include, for example, (meth) acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and hexyl methacrylate, For example, it can be obtained by a copolymerization reaction with (meth) acrylic acid hydroxyalkyl esters such as β-hydroxyethyl acrylate and β-hydroxyethyl methacrylate. In addition to these monomers, aromatic vinyl compounds such as styrene can be used if necessary.

The polyester polyol is, for example, a dibasic acid such as maleic acid, fumaric acid, succinic acid, adipic acid, sebacic acid, azelaic acid, phthalic acid, isophthalic acid, terephthalic acid or trimellitic acid, and a divalent divalent acid. To those obtained by a condensation reaction with a tetrahydric polyhydric alcohol. Here, as the dihydric to tetrahydric polyhydric alcohol, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,
Examples include 5-pentanediol, 1,6-hexanediol, neopentyl glycol, hydrogenated bisphenol A, trimethylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, castor oil and the like. Further, for example, a higher fatty acid such as a coconut oil fatty acid, a linseed oil fatty acid, a soybean oil fatty acid, a cottonseed oil fatty acid, a tung oil fatty acid and a castor oil fatty acid may be blended in the acid component to form an oil-modified polyester polyol.

The polyether polyol is obtained, for example, by using ethylene glycol, propylene glycol, glycerin, pentaerythritol or the like as an initiator, and ethylene oxide, propylene oxide or a mixture thereof to undergo ring-opening addition polymerization. Or, for example, polytetramethylene ether glycol obtained by ring-opening polymerization of tetrahydrofuran can be used.

In addition to the above, polyether ester polyol, polybutadiene polyol and polyisoprene polyol can also be used as the polyol. Examples of the above polyether ester polyol include those obtained by reacting the above polyether polyol as a raw material with a polybasic acid to form a polyester, and molecules obtained by a ring-opening copolymerization reaction between an epoxy compound and an acid anhydride. Examples thereof include those having both polyether and polyester segments.

Polyisocyanate is a crosslinking agent for polyols and has two or more isocyanate groups in one molecule. Specifically, aliphatic diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate and hexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate; xylylene diisocyanate, metaxylylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene. Aromatic diisocyanates such as diisocyanates; adducts of diisocyanates with polyhydric alcohols; cyclized polymers of diisocyanates; and burette type adducts.

The above-mentioned polyol and polyisocyanate are usually mixed in such a ratio that the ratio of hydroxyl groups to isocyanate groups is about 0.8 to 1.2 isocyanate groups per one hydroxyl group.

The barium sulfate used in the coating composition of the present invention contains barium sulfate as a main component (containing 90% or more) and is coated with SiO ₂ , Al ₂ O ₃ or the like if necessary, and has an average particle diameter of 0. .1 to 1 .mu.m, preferably 0.2 to 0.5 .mu.m. If the average particle diameter is out of the above range, bubbles contained in the cured coating film increase and the surface gloss of the coating film decreases, which is not preferable.

The compounding ratio of barium sulfate is 80 to 12 per 100 parts by weight of the above isocyanate-curable resin (total amount of polyol and polyisocyanate) (solid content).
It is 0 part by weight, preferably 90 to 110 parts by weight. If the compounding ratio is out of the above range, there are disadvantages that the amount of bubbles contained in the cured coating film increases and a coating film having high surface gloss cannot be obtained.

The coating composition of the present invention can be used as a solution prepared by dissolving or dispersing the above isocyanate-curable resin in an organic solvent. Examples of the organic solvent include esters such as ethyl acetate, butyl acetate and cellosolve acetate, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, for example, aromatic hydrocarbons such as toluene and xylene, for example, Examples thereof include cyclic ethers such as tetrahydrofuran and dioxane. Among these organic solvents, acetone, cellosolve acetate, methyl ethyl ketone, tetrahydrofuran, dioxane and the like are preferable.

In addition to the above, the coating composition of the present invention may contain a color pigment, a defoaming agent, a curing catalyst (such as an amine compound and a metal compound), and other coating additives.

In the coating film forming method of the present invention, the above-mentioned chipping-resistant top coating composition is applied to an object to be coated, and a cured coating film of 50 to 300 is formed.
It can be carried out by spray coating so as to have a thickness of 100 μm, preferably 100 to 200 μm. If the film thickness is less than 50 μm, the chipping resistance will be poor because the impact absorption capacity of the coating film due to chipping will be poor. On the other hand, even if it exceeds 300 μm, no further improvement in chipping resistance will be recognized, and product cost and weight reduction will be achieved. It will be disadvantageous.

Examples of the object to be coated include ordinary metals (materials or molded products) such as iron, steel, alloy steel, aluminum and aluminum alloys, zinc, galvanized steel, zinc alloy and tin plated steel. Further, those obtained by subjecting these metal surfaces to shot blasting, sand blasting, or surface treatment with zinc phosphate, iron phosphate, chromium or the like can also be used.

[0025]

The present invention will be described in detail below with reference to examples. In addition, "part" and "%" in an Example mean a "weight part" and "weight%", respectively.

Production Example of Paint 1 Haripol F-16 (trade name, manufactured by Harima Chemicals Co., Ltd.)
Alkyd polyol) 20 parts, titanium white JRNC (manufactured by Teika Co., Ltd., trade name, titanium white) 12 parts, carbon black MA-100 (manufactured by Mitsubishi Kasei Co., Ltd., trade name, carbon black) 2 parts, Variace B-30 (manufactured by Sakai Chemical Industry Co., Ltd., trade name, average particle diameter 0.3 μm,
40 parts of Al ₂ O ₃ .SiO ₂ surface-treated) and 10 parts of xylene were ball mill dispersed to obtain a pigment paste.
Then add 14 parts of Halipol F-16 (same as above), 5 parts of xylene, Neostern U-100.
(Nitto Kasei Co., Ltd., tin catalyst) 0.005 part, and Duranate TPA-100 (Asahi Kasei Co., Ltd., trade name, polyisocyanate) 16.5 parts are mixed to obtain a solid content of 75%. Thus, coating material 1 was obtained by diluting with xylene.

Production Example of Paint 2 A paint 2 was produced in the same manner as the paint 1 except that the amount of variace B-30 in the paint 1 was changed to 32 parts.

Production Example of Paint 3 A paint 3 was produced in the same manner as the paint 1 except that the amount of the variace B-30 compounded in the paint 1 was 49 parts.

Production Example of Paint 4 In Paint 1, Variace B-34 (Sakai Chemical Industry Co., Ltd.)
(Trade name, barium sulfate, average particle diameter 0.3 μm)
A coating material 4 was prepared in the same manner as the coating material 1 except that the compounding amount was 40 parts.

Production Example of Paint 5 Paint 5 was obtained in the same manner as Paint 1 except that 28 parts of Variace B-30 was used.

Production Example of Paint 6 Paint 6 was obtained in the same manner as Paint 1 except that 53 parts of Variace B-30 was used.

Production Example of Paint 7 Instead of VARIACE B-30 in Paint 1, the same amount of Varifine BF-20 (manufactured by Sakai Chemical Industry Co., Ltd., trade name, barium sulfate, average particle size 0.03 μm) was used. A coating material 7 was obtained in the same manner as the coating material 1 except for the above.

Production Example of Paint 8 In the paint 1, Barita BA was used instead of Variace B-30.
A coating material 8 was obtained in the same manner as in the coating material 1 except that the same amount was used (trade name, barium sulfate, average particle diameter 1.8 μm, manufactured by Sakai Chemical Industry Co., Ltd.).

Production Example of Paint 9 Except that the same amount of Neolite SPT (manufactured by Takehara Chemical Industry Co., Ltd., trade name, calcium carbonate, average particle diameter 0.15 μm) was used in place of Variace B-30 in Paint 1. A paint 9 was obtained by manufacturing in the same manner as the paint 1.

Production Example of Paint 10 In place of Variace B-30 in Paint 1, the same amount of barge clay 10 (manufactured by Shiraishi Calcium Co., Ltd., trade name, aluminum silicate, average particle size 0.9 μm) was used. A coating material 10 was obtained in the same manner as the coating material 1 except for the above.

Production Example of Paint 11 In place of Variace B-30 in Paint 1, the same amount of Micro-S L-1 (manufactured by Nippon Talc Co., Ltd., trade name, hydrous magnesium silicate, average particle size 1.5 μm) was used. A coating material 11 was obtained in the same manner as in the coating material 1 except for the above.

Preparation of Coated Plate A shot-blasted steel plate was coated to obtain a coating film having a thickness of 150 to 200 μm. Then, after leaving it at 20 ° C for 20 minutes, 60
Heating was carried out at 0 ° C for 20 minutes. The results are summarized in Table 1.

[0038]

[Table 1]

Gloss: specular reflectance of 60 degrees

Coating state: The presence or absence of cracks and pinholes on the coating surface was visually determined according to the following. ◎ (no cracks and pinholes are observed), ○ (some pinholes are recognized), △ (rocks and pinholes are recognized),
× (Warms and pinholes are noticeable.)

Chipping resistance: 500 g of No. 6 silica sand was added to 3
Hit the coated surface with a pressure of kg / cm ² . Similarly, what was repeated 5 times was visually evaluated according to the following. ○ (It is good that only a few scratches due to impact are observed on part of the coating film.) △ (Scratches and peeling due to impact are observed on the coating film) × (Scratches and peeling due to impact on the coating film Remarkably large.)

Salt spray resistance: JIS K5400
The test was carried out according to. (The coated plate used was one in which the coating film was cross-cut with a cutter so as to reach the steel plate.)
Judgment was made by observing the width of rust from the cut portion, and those with a width of 3 mm or less were evaluated as ◯, and those with a width of 3 mm or more were evaluated as x.

[0043]

Since the coating composition of the present invention has the above-mentioned constitution, a coating film having high gloss and excellent chipping resistance can be formed.

Claims (2)

[Claims] 1. A chipping-resistant top coating composition comprising an isocyanate curable resin and 80 to 120 parts by weight of barium sulfate having an average particle diameter of 0.1 to 1 μm per 100 parts by weight of the resin. 2. An isocyanate-curable resin is coated with barium sulfate having an average particle size of 0.1 to 1 μm as the resin 1 to be coated.
A chipping-resistant top-coating coating composition containing 80 to 120 parts by weight per 100 parts by weight has a coating film thickness of 50 to 3 when cured.
A coating film forming method, characterized in that spray coating is carried out so that the thickness becomes 00 μm.